Applicants claim, under 35 U.S.C. .sctn. 119, the benefit of priority of the filing date of May 24, 1991, of a European application, copy attached, Serial Number 91108389.7, filed on the aforementioned date, the entire contents of which are incorporated herein by reference.
The invention relates to an optical device for coupling and/or decoupling beams of light, having an integrated optical component. Devices of this kind are increasingly used in length and angle measuring technology, to enable producing the smallest possible position measuring instruments that are as invulnerable as possible to malfunction.
A small-sized position measuring instrument is for instance the subject of German Patent DE 36 25 327 Cl. From this patent, and from the prior art discussed in it, it is known in principle to introduce light into fiberoptical waveguides of integrated optical circuits with the aid of coupling gratings. In the prior art, a relatively wide spacing (several millimeters) is necessary between the gauge and the integrated optical component, or between the diffraction gratings, in order to attain a spatial separation of the two measuring beams at the locations of the coupling gratings.
It can also be learned from the prior art that coupling or decoupling gratings are subject to complicated mathematical relationships and typically extend elliptically or parabolically or are even more complicated in structure, as can be seen also from German Patent Disclosure Document DE 39 28 064 Al.
As a consequence of all of these factors, virtually no equipment that includes actually manufactured coupling or decoupling gratings has thus far been developed in actual practice, even though the need for such miniaturized position measuring instruments exists.
The absence of a miniaturized position measuring instrument leads to many disadvantages in prior art devices. For example, prior art instruments have beams which have a large angular separation that when they are coupled into waveguides the waveguides are separated by an amount that requires an extensive coupler to combine the two beams. Having the coupling elements relatively far apart requires the distance between diffraction gratings used to produce the beams to be relatively far apart. This arrangement results in an increase in the sensitivity of the system to tilting and twisting which can cause measurement errors.
Furthermore, the optical travel distances and angular separations are relatively large which require the measurement system to be relatively large in all coordinate directions, such as the Z direction. Also, the large angular separations result in more than one coupling grating being required.